Wire electrical discharge machine and machining program editor

ABSTRACT

A machining program editor that edits a machining program in which a machining path for a wire electrode of a wire electrical discharge machine is set, the machining program editor including: a path determination unit configured to determine whether or not the machining path includes a linear path section that crosses a boundary line between a thick portion of a workpiece and a thin portion of the workpiece, a thickness of the thin portion being smaller than a thickness of the thick portion in an extending direction of the wire electrode; and a path compensator configured to compensate the machining path so as to form, in the thin portion over a predetermined distance, a protrusion projecting outward from the boundary line when the path determination unit determines that the linear path section is included.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a DIVISIONAL Application of U.S. patentapplication Ser. No. 16/811,695, filed on Mar. 6, 2020, which is basedupon and claims the benefit priority from Japanese Patent ApplicationNo. 2019-044915 filed on Mar. 12, 2019, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wire electrical discharge machine anda machining program editor.

Description of the Related Art

A wire electrical discharge machine is a type of machine tool. A wireelectrical discharge machine performs electrical discharge machining ona workpiece by generating discharge sparks between a wire electrode andthe workpiece while producing relative motion between the wire electrodeand the workpiece. Thereby, the object to be processed, i.e., theworkpiece, is machined into a designated shape.

The wire electrode of the wire electrical discharge machine relativelymoves along a machining path with respect to the workpiece during theimplementation of electrical discharge machining. The machining path isset in a program that is loaded and executed by the wire electricaldischarge machine. Thus, the operator can machine the workpiece into adesired shape.

SUMMARY OF THE INVENTION

Electrical discharge machining performed by the wire electricaldischarge machine may have a problem when the workpiece has a step atwhich the thickness changes. The problem is, for example, reducedaccuracy of electrical discharge machining at the step in the workpiece,disconnection of the wire electrode at the step and the like. To dealwith the above problem, Japanese Laid-Open Patent Publication No.2007-144567 proposes a configuration in which the machining condition isautomatically changed so as to be suitable for the positions of steps.Examples of the machining condition include a set value of the voltageapplied to the wire electrode.

However, when a setting of the machining condition is changed duringelectrical discharge machining, the amount of removal from the workpieceduring electrical discharge changes abruptly due to the change of thesetting. As a result, unintended streak-like flaws may form on thesurface of the workpiece after the electrical discharge machining. Inthis way, changing only the machining condition at the position of thestep cannot achieve the operator's intended accuracy in machining theworkpiece.

It is therefore an object of the present invention to provide a wireelectrical discharge machine and a machining program editor, whichenables implementation of electrical discharge machining whilesuppressing generation cf flaws around a step in a workpiece.

One aspect of the present invention resides in a wire electricaldischarge machine that machines a workpiece using a wire electrode, thewire electrical discharge machine comprising; a drive control unitconfigured to move the wire electrode relative to the workpiece along amachining path set in a machining program; a path determination unitconfigured to determine whether or not the machining path includes alinear path section that crosses a boundary line between a thick portionof the workpiece and a thin portion of the workpiece, a thickness of thethin portion being smaller than a thickness of the thick portion in anextending direction of the wire electrode; and a path compensatorconfigured to compensate the machining path so as to form, in the thinportion over a predetermined distance, a protrusion projecting outwardfrom the boundary line when the path determination unit determines thatthe linear path section is included.

Another aspect of the present invention resides in a machining programeditor that edits a machining program in which a machining path for awire electrode of a wire electrical discharge machine is set, themachining program editor comprising: a path determination unitconfigured to determine whether or not the machining path includes alinear path section that crosses a boundary line between a thick portionof a workpiece and a thin portion of the workpiece, a thickness of thethin portion being smaller than a thickness of the thick portion in anextending direction of the wire electrode; and a path compensatorconfigured to compensate the machining path so as to form, in the thinportion over a predetermined distance, a protrusion projecting outwardfrom the boundary line when the path determination unit determines thatthe linear path section is included.

According to the present invention, it is possible to provide a wireelectrical discharge machine and a machining program editor, whichenable implementation of electrical discharge machining whilesuppressing generation of flaws around a step in a workpiece.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a wire electricaldischarge machine according to a first embodiment;

FIG. 2 is a block diagram showing part of the electrical configurationof the wire electrical discharge machine according to the firstembodiment;

FIG. 3 is a block diagram schematically showing the configuration of acontroller according to the first embodiment;

FIG. 4 is a flowchart for explaining an example of a flow of processingperformed by the wire electrical discharge machine according to thefirst embodiment;

FIG. 5 is a perspective view of a workpiece in the first embodiment;

FIG. 6 is a top view of the workpiece in the first embodiment;

FIG. 7 is a top view of the workpiece showing a machining pathcompensated by a path compensator according to the first embodiment;

FIG. 8 is a top view showing the workpiece that has been completed up toa machining step one step before a finishing step;

FIG. 9A is a perspective view showing the workpiece when the finalfinishing step has been completed;

FIG. 9B is a perspective view showing an example of a workpiece that hasbeen subjected to a related art machining process;

FIG. 10A is a top view showing a workpiece that has been completed up toa machining step one step before a finishing step in a modified example1-1;

FIG. 103 is a top view showing another example of a workpiece machinedin the modified example 1-1;

FIG. 11 is a block diagram showing a configuration of a machiningprogram editor according to a second embodiment; and

FIG. 12 is a flowchart for explaining an exemplary flow of a processperformed by the machining program editor of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedetailed below by describing preferred embodiments with reference to theaccompanying drawings. The orientations of the axes in the followingdescription are as shown in the drawings.

First Embodiment

FIG. 1 is an overall configuration diagram of a wire electricaldischarge machine 10 according to the first embodiment.

The wire electrical discharge machine 10 is a machine tool that performselectrical discharge machining on a workpiece 14 (FIG. 5 ) along amachining path 16 (FIG. 6 ) by generating discharge sparks between awire electrode 12 and the workpiece 14 while relatively moving the wireelectrode 12 with respect to the workpiece 14. Hereinbelow, the “wireelectrical discharge machine 10” is also simply referred to as “themachine 10”. “Electrical discharge machining” is also simply referred toas “machining”.

The machine 10 includes a main body 18 and a controller 20. The mainbody 18 includes a supply system 22 that feeds the wire electrode 12 tothe workpiece 14 which is an object to be machined, a collection system24 that collects the wire electrode 12 having passed through theworkpiece 14, and a tank 26 for storing a dielectric working fluid.

The supply system 22 includes a wire bobbin 28, a brake roller 30, abrake motor 32, a torque motor 34, a tension detector 36 and a firstwire guide 38. The-wire electrode 12 is wound on the wire bobbin 28,which is applied with torque by the torque motor 34. The brake roller 30applies a braking force by friction to the wire electrode 12 as it isapplied with a brake torque by the brake motor 32. The tension detector36 detects the tension of the wire electrode 12. The first wire guide 38is immersed in the dielectric working fluid inside the tank 26 andguides the wire electrode 12 above the workpiece 14.

The collection system 24 includes a pinch roller 40, a feed roller 42, awire collection box 44, and a second wire guide 46. The pinch roller 40and the feed roller 42 are arranged to pinch and transfer the wireelectrode 12, and the transferred wire electrode 12 is collected intothe wire collection box 44. The second wire guide 46 is immersed in thedielectric working fluid inside the tank 26, and guides the wireelectrode 12 below the workpiece 14.

FIG. 2 is a block diagram showing part of the electric configuration ofthe wire electrical discharge machine 10 according to the firstembodiment.

The machine 10 can transfer the wire electrode 12 in the Z-axisdirection by the supply system 22 and the collection system 24. Further,the first wire guide 38 and the second wire guide 46 are each connectedto a U-axis servomotor and a V-axis servomotor (not shown). Thereby, themachine 10 can move each of the first wire guide 38 and the second wireguide 46 along the U axis or the V axis (FIG. 1 ).

A support portion 50 for supporting the workpiece 14 is provided insidethe tank 26 (see FIG. 1 ). The support portion 50 is, for example, atable. In this embodiment, the wire electrode 12 moves relatively as thesupport portion 50 moves in actuality. In order to realize this, in thepresent embodiment, an X-axis servomotor 48 x and a Y-axis servomotor 48y are connected to the support portion 50. The X-axis servomotor 48 x isa servomotor 48 that rotates to move the support portion 50 along theX-axis. The Y-axis servomotor 48 y is a servomotor 48 that rotates tomove the support portion 50 along the Y-axis.

FIG. 3 is a block diagram schematically showing the configuration of thecontroller 20 of the first embodiment.

The controller 20 of the machine 10 is, for example, a CNC (ComputerNumerical Control Unit), and includes a processor 52 capable ofexecuting arithmetic processing and a memory 54 storing a machiningprogram. Further, the controller 20 includes operation buttons forsending instructions to the machine 10 and a touch panel display unit 56for displaying machining progress information and the like on a screen.

“The machining program” is a program in which the route of the relativemovement of the wire electrode 12 when performing electrical dischargemachining on the workpiece 14 is set. The “route of the relativemovement of the wire electrode 12 when performing electrical dischargemachining on the workpiece 14” may be also referred to as “the machiningpath 16”. The machining program is created by the operator prior to theimplementation of machining.

The screen of the touch panel display unit 56 is, for example, a liquidcrystal screen equipped with a touch panel. The operation buttons andinformation displayed on the screen of the touch panel display unit 56may be changed as appropriate. The operator can send instructions to thesupply system 22 and the collection system 24 of the main body 18through the touch panel display unit 56. Examples of the instructionsthe operator sends to the main body 18 include a command to startmachining or a command to change a setting of the machining conditionfor electrical discharge machining. Thus, the touch panel display unit56 not only functions to notify information to the operator but alsoacts an operation unit for the operator to give instructions to themachine 10.

The controller 20 further includes a drive control unit 58 forcontrolling the relative movement of the wire electrode 12 based on themachining path 16 read from the machining program, a machining conditionsetter 60 for setting the machining conditions, and a machining controlunit 62 for controlling implementation of electrical discharge machiningaccording to the machining condition In the present embodiment, each ofthe drive control unit 58, the machining condition setter 60 and themachining control unit 62 is one of the functional units included in theprocessor 52.

The drive control unit 58 controls the rotation of each of the X-axisservomotor 48 x and the Y-axis servomotor 48 y based on the machiningprogram to move the support portion 50 supporting the workpiece 14.Thereby, the wire electrode 12 relatively moves along the machining path16 designated in the machining program.

The machining condition setter 60 sets the machining condition formachining the workpiece 14 by reading a predetermined program stored inthe memory 54 or receiving operator's instructions. In the presentembodiment, “the machining condition” indicates a combination of controlparameters for specifying the details in controlling spark machining,including the magnitude of the voltage applied to the wire electrode 12and the pause time of application of the voltage.

For example, the machining control unit 62 applies voltage to the wireelectrode 12 based on the machining condition determined by themachining condition setter 60. As a result, electrical discharges aregenerated between the wire electrode 12 and the workpiece 14 in thedielectric working fluid stored in the tank 26. Thus, by generatingsparks, the machine 10 can remove unnecessary parts close to the wireelectrode 12 from the workpiece 14.

When machining on the workpiece 14, the machine 10 causes the machiningcontrol unit 62 to generate electrical discharges while making the drivecontrol unit 58 produce relative movement of the wire electrode 12 alongthe machining path 16. The machining conditions including the voltageapplied to the wire electrode 12 when machining are set by the machiningcondition setter 60.

The machine 10 according to the present embodiment includes a pathdetermination unit 64 and a path compensator 66 in addition to the drivecontrol unit 58, the machining condition setter 60 and the machiningcontrol unit 62. The path determination unit 64 and the path compensator66 are one of the functional units included in the processor 52, likethe drive control unit 58 and the like.

The path determination unit 64 determines whether the machining path 16includes a linear path section crossing a boundary line 68. Here, theboundary line 68 is a line that lies along the boundary that separatesthe workpiece 14 into a thick portion 70 and a thin portion 72 whosethickness in the extending direction of the wire electrode 12 is smallerthan that of the thick portion 70. When making determination, the pathdetermination unit 64 may refer to information stored in the memory 54as appropriate. The information the path determination unit 64 refers tois, for example, the machining program in which the machining path 16 isset, and CAD data indicating the shape of the workpiece 14.

The path compensator 66 compensates the machining path 16 according tothe result of the determination from the path determination unit 64.Specifically, the path compensator 66 compensates the machining path 16so as to form, in the thin portion 72 over a predetermined distance 76,a protrusion 74 projecting outward from the boundary line 68 (FIG. 8 ).Here, the “outward” is the direction that is orthogonal to both thedirection of the machining path 16 and the extending direction of thewire electrode 12, and that goes toward the nearest endface of theworkpiece 14 as viewed from the point on the machining path 16.

FIG. 4 is a flowchart for explaining an example of a flow of processingperformed by the wire electrical discharge machine 10 according to thefirst embodiment;

Now, an example of a flow of processing executed by the machine 10 whenmachining the workpiece 14 will be described with reference to FIG. 4 .The process shown in FIG. 4 is started when, for example, the operatorselects a machining program to start machining (START).

FIG. 5 is a perspective view of a workpiece 14 of the first embodiment.FIG. 6 is a top view of the workpiece 14 of the first embodiment.

For example, as shown in FIG. 5 , it is assumed that the workpiece 14has a step in the Z-axis direction (the extending direction of the wireelectrode 12). In this case, the workpiece 14 includes two portionsseparated at the boundary line 68 where the step is formed, i.e., thethick portion 70 and the thin portion 72 whose thickness in the Z-axisdirection is relatively smaller than that of the thick portion 70.

As described above, the path determination unit 64 determines whetherthe machining path 16 includes a linear path section crossing theboundary line 68 (Step S1).

It is assumed that the workpiece 14 has the shape as shown in FIGS. 5and 6 and that the machining path 16 shown in FIG. 6 has been set in themachining program. As understood from FIG. 6 , the machining path 16includes a first linear path section 78 parallel to the X-axis, a secondlinear path section 80 also extending parallel to the X-axis directionand a third linear path section 82 that extends parallel to the Y-axisto connect the first linear path section 78 and the second linear pathsection 80. Among these, the first linear path section 78 and the secondlinear path section 80 intersect the boundary line 68 between the thickportion 70 and the thin portion 72 at intersections 84 and 84′,respectively.

Accordingly, the path determination unit 64 determines that themachining path 16 illustrated in FIG. 6 “includes a linear path sectioncrossing the boundary line 68”. Here, the “linear path section crossingthe boundary line 68” refers to each of the first linear path section 78and the second linear path section 80.

It should be noted that the path determination unit 64 does not need tomake a determination for the boundary lines 68 of all of the steps ofthe workpiece 14. For example, the path determination unit 64 may make adetermination only for the steps having a thickness difference equal toor greater than a predetermined amount at step S1. The predeterminedamount here may be an amount designated in advance by the operator.

If it is determined “NO” at step S1, the machine 10 performs normalmachining (step S7). The normal machining refers to a process in which aroughing step and a finishing step are performed along the originalmachining path 16. The machine 10 may wait for the execution of step 57until the operator instructs the start of the machining.

FIG. 7 is a top view of the workpiece 14 having the machining path 16compensated by the path compensator 66 according to the firstembodiment.

When the path determination unit 64 determines that a linear pathsection crossing the boundary line 68 is included, the pathdetermination unit 64 outputs the determination result to the pathcompensator 66. Then, the path compensator 66 compensates the machiningpath 16 such that the protrusion 74 (FIG. 8 ) projecting outward fromthe boundary line 68 is formed in the thin portion 72 over thepredetermined distance 76 (Step S2). Here, the Y-axis positive directionis the outward direction on the first linear path section 78 side of theworkpiece 14, whereas the Y-axis negative direction is the outwarddirection on the second linear path section 80 side of the workpiece 14.

By compensating the machining path 16, the path compensator 66 replacesa part of the first linear path section 78 with a compensated pathsection 86. Similarly, the path compensator 66 replaces a part of thesecond linear path section 80 with a compensated path section 86.Hereinafter, for distinction, the compensated path section 86 thatreplaces a predetermined range of the second linear path section 80 mayalso be referred to as a “compensated path section 86′”.

The compensated path section 86 generated to replace a part of the firstlinear path section 78 starts from the intersection 84. The compensatedpath section 86 further includes, as a halfway point, a first point 88located on the outer side of the intersection 84, and includes, as anend point, a second point 90 that is a point on the first linear pathsection 78 in the thin portion 72 and is separated by the predetermineddistance 76 from the intersection 84. In this embodiment, the firstpoint 88 resides on the boundary line 68. Therefore, a line segmentconnecting the intersection 84 and the first point 88 is orthogonal tothe first linear path section 78. The compensated path section 86 inthis embodiment is the shortest route formed by connecting theintersection 84, the first point 88 and the second point 90 in thisorder.

The compensated path section 86′ generated to replace a part of thesecond linear path section 80 ends at the intersection 84′. Thecompensated path section 86′ further includes, as a halfway point, afirst point 88′ located on the outer side of the intersection 84′, andincludes, as a start point, a second point 90′ that is a point on thesecond linear path section 80 in the thin portion 72 is separated by thepredetermined distance 76 from the intersection 84′. In the presentembodiment, the first point 88′ resides on the boundary line 68.Therefore, a line segment connecting the intersection 84′ and the firstpoint 88′ is orthogonal to the second linear path section 80. Thecompensated path section 86′ in this embodiment is the shortest routeformed by connecting the second point 90′, the first point 88′ and theintersection 84′, in this order.

When the path compensator 66 compensates the machining path 16, theinformation on the compensated machining path 16 is stored in the memory54 together with the machining program in which the original machiningpath 16 is set. Hereinafter, for distinction, the machining path 15before being compensated by the path compensator 66 may be referred toas the “original machining path 16”. For the same reason, the machiningpath 16 compensated by the path compensator 66 may be referred to as the“compensated machining path 16”.

The drive control unit 58 waits for a machining start instruction (stepS3). The machine 10 may start machining as the operator manually gives astart instruction or may start machining automatically at a fixed timewhen the time set on the timer is reached.

The workpiece 14 of the present embodiment is processed through twostages of machining, namely “roughing” and “finishing”. For each stageof machining, an appropriate offset between the wire electrode 12 andthe workpiece 14 is specified taking into account the size of the wireelectrode 12. In the present embodiment, the drive control unit 58specifies the offset. Of the roughing and finishing stages, at least thefinishing is repeated a multiple number of times. In the presentembodiment, the finishing executed last is also described as “a finalfinishing step”.

When the machining start instruction is given, the drive control unit 58determines whether or not the next machining step to be executed is thefinal finishing step (step S4). In the present embodiment, at least thefirst machining step after the start of the machining cycle is aroughing step. Therefore, before the execution of the first roughingstep, the drive control unit 58 may set the determination result to “NO”and make the determination at step S4 substantially unnecessary.

When the machining to be executed next is not the final finishing step,the drive control unit 58 moves the wire electrode 12 relative to theworkpiece, along the compensated machining path 16 (step At this time,the machining control unit 62 performs machining based on the machiningcondition set by the machining condition setter 60. Thereby, theworkpiece 14 is gradually machined into shape along the compensatedmachining path 16.

FIG. 8 is a top view of the workpiece 14 that has been processed up tothe machining step one step before the final finishing step.

At the point of time when the machining step one step before the finalfinishing step is completed, the above-mentioned protrusion 74 is formedon the surface of the thin portion 72 on the Y-axis positive side. Theprotrusion 74 has an approximately triangular prism-like form with asubstantially right triangular base having, as vertices, theintersection 84, the first point 88 located on the line extendingorthogonally to the first linear path section 78 from the intersection84 and the second point 90 located on the machining path 16 andseparated by the predetermined distance 76 from the intersection 84. Asurface 74 a of the protrusion 74 on the thick portion 70 side extendsalong the boundary line 68.

Similarly, at the point of time when the machining step one step beforethe final finishing step is completed, a protrusion 74′ is formed on theY-axis negative side of the thin portion 72. The protrusion 74′ has anapproximately triangular prism-like form with a substantially righttriangular base having, as vertices, the intersection 84′, the firstpoint 88′ located on the line extending orthogonally to the secondlinear path section 80 from the intersection 84′ and the second point90′ located on the machining path 16 and separated by the predetermineddistance 76 from the intersection 84′. A surface 74 a′ of the protrusion74′ on the thick portion 70 side extends along the boundary line 68.

FIG. 9A is a perspective view of the workpiece 14 in a state where thefinal finishing step has been completed.

When the drive control unit 58 determines at step S4 that the machiningstep to be executed next is the final finishing step, the drive controlunit 58 moves the wire electrode 12 relative to the workpiece along theoriginal machining path 16 in the final finishing step (step S6). Atthis time, the machining control unit 62 performs machining based on themachining condition set by the machining condition setter 60. Thereby,in the final finishing step, the protrusions 74 and 74′ are removed fromthe workpiece 14 so that the workpiece 14 as shown in FIG. 9A isobtained as a complete product (END).

FIG. 9B is a view showing an example of the workpiece 14 that has beenprocessed in the conventional technique.

Now, a description will be given of a problem in the related art thathas occurred when the workpiece 14 is machined. In the conventionalmachine 10, when the wire electrode 12 linearly passes through theboundary line 68 while machining the workpiece 14, the removal amountper unit time of unnecessary parts from the workpiece 14 sharplychanges, depending on the difference in thickness between the thickportion 70 and the thin portion 72.

Specifically, when the wire electrode 12 passes through the boundaryline 68 on the first linear path section 78, the removal amount per unittime of unnecessary parts from the workpiece 14 sharply decreases in atransition from machining on the thick portion 70 to machining on thethin portion 72. Further, when the wire electrode 12 passes through theboundary line 68 on the second linear path section 80, the removalamount per unit time of unnecessary parts from the workpiece 14 sharplyincreases in a transition from machining on the thin portion 72 tomachining on the thick portion 70.

The sudden change in the removal amount per unit time of unnecessaryparts from the workpiece 14 means that the frequency of discharge sparksgenerated between the wire electrode 12 and the workpiece 14 changessignificantly. When the frequency of discharge sparks changes suddenly,the average voltage of the wire electrode 12 becomes temporarilyunstable. As a result, the machining accuracy temporarily degrades, andfor example, streak-like flaws 92 extending in the Z-axis direction areformed on the surface of the workpiece 14, as shown in FIG. 9B.

Regarding the above problem, in the present embodiment, in the machiningat the final finishing step, the amount of removal of at least part ofthe protrusion 74 (the protrusion 74′) in the range of the unit movementin which the wire electrode 12 can move relative to the workpiece in theunit time, is included in the amount of removal per unit time.Accordingly, when the workpiece 14 is machined along the first linearpath section 78 (second linear path section 80) at the final finishingstep, the removal amount per unit time of the workpiece 14 across theboundary line 68 is restrained from changing abruptly.

Further, the shape of the protrusion 74 is an approximately triangularprism having a substantially right triangular base formed by connectingthe intersection 84, the first point 88 and the second point 90.Therefore, as the protrusion 74 is removed from the intersection 84toward the second point 90, the removal amount per unit time of theworkpiece 14 gradually decreases. Similarly, as the protrusion 74′ isremoved from the second point 90′ toward the intersection 84′, theremoval amount per unit time of the workpiece 14 gradually increases.

Thus, in the present embodiment, even after the wire electrode 12 haspassed through the boundary line 68 along the original machining path 16at the final finishing step, a sudden change of the removal amount perunit time of the workpiece 14 can be avoided.

As described above, according to the machine 10 of the presentembodiment, the workpiece 14 can be machined while suppressinggeneration of the flaws 92 around the stepped portions of the workpiece14.

In the present embodiment, it is preferable that the area of the surface74 a of the protrusion 74 and the area of the surface 74 a′ of theprotrusion 74 are set so that the removal amount per unit time of theworkpiece 14 is the same immediately before and after passing throughthe boundary line 68. Therefore, it is preferable that the pathcompensator 66 is configured to set the distance between theintersection 84 and the first point 88 and the distance between theintersection 84′ and the first point 88′ so that the removal amount perunit time of the workpiece 14 is the same immediately before and afterpassing through the boundary line 68. Thus, it is possible to suppressoccurrence of an abrupt change in the removal amount per unit time ofthe workpiece 14 at the boundary line 68, in the most optimal manner.

MODIFIED EXAMPLES

Though the above embodiment has been described as one example of thepresent invention, it goes without saying that various modifications andimprovements can be added to the above embodiment. It is apparent fromthe scope of claims that modes added with such modifications andimprovements should be incorporated in the technical scope of theinvention.

Modified Example 1-1

FIG. 10A is a top view showing a workpiece 14 that has been completed upto the machining step one step before the finishing step according to amodified example 1-1. FIG. 103 is a top view of a workpiece 14 showinganother example of the modified example 1-1.

In the first embodiment (FIG. 8 ), the shape of the base of theprotrusion 74 is substantially triangular. The shape of the base may bechanged from the shape shown in FIG. 8 into those shown in FIGS. 10A and10B. FIG. 10A shows an example where the first point 88 resides on thethick portion 70 side with respect to the intersection 84. FIG. 10Bshows an example where the shape of the base of the protrusion 74 is nota substantially triangular shape but a trapezoidal shape. Also in thismodified example, similarly to the first embodiment, it is possible tosuppress generation of the flaws 92 on the workpiece 14.

Modified Example 1-2

In the first embodiment, the protrusions 74 and 74′ are removed at thefinal finishing step. The protrusions 74 and 74′ may be removed at afinishing step other than the final finishing step when a plurality offinishing steps are included in the machining cycle. In other words, thedrive control unit 58 may move the wire electrode 12 relative to theworkpiece along the compensated machining path 16 until a predeterminedmachining step, and then move the wire electrode 12 relative to theworkpiece along the original machining path 16 at the machining stepsafter the predetermined machining step.

The “predetermined machining step” may include, among the plurality ofmachining steps, the final roughing step (the machining step one stepbefore the first finishing step) to the finishing step one step beforethe final finishing step.

In finishing steps, the workpiece is machined under machining conditionthat is more limited than in roughing steps. Therefore, it can be saidthat a finishing step is less likely to generate flaws 92 than roughingsteps. Additionally, the machining condition for a finishing step, whichis more limited than in roughing steps, may make removing theprotrusions 74 and 74′ and completely tiding up the surface of theworkpiece 14 during the machining process, more difficult in some casesdepending on the settings of the machining condition.

From the above viewpoints, in this modified example, the removal of theprotrusions 74 and 74′ is allowed before the execution of the finalfinishing step. Thus, the risk of formation of the flaws 92 can bereduced, and the risk of traces of the protrusions 74 and 74′ remainingon the finished product of the workpiece 14 can be reduced as comparedto the first embodiment.

Modified Example 1-3

When the workpiece 14 is being processed by electrical dischargemachining, particularly in a roughing step performed at the beginning ofa machining cycle, the average voltage applied to the wire electrode 12becomes unstable around the boundary line 68 between the thick portion70 and the thin portion 72. Similarly, in the roughing step performed atthe beginning of the machining cycle, the frequency of discharge sparksgenerated between the wire electrode 12 and the workpiece 14 becomesunstable around the boundary line 68 between the thick portion 70 andthe thin portion 72. Therefore, by monitoring at least one of theaverage voltage of the wire electrode 12 and the frequency of thegenerated discharge sparks, it is possible to determine that the wireelectrode 12 is approaching the boundary line 68.

In relation to the above, the path determination unit 64 may detect theboundary line 68 while the wire electrode 12 is moving relative to theworkpiece along the machining path 16 to machine the workpiece 14. Inthis case, the path determination unit 64 may detect the position of theboundary line 68 based on the average voltage of the wire electrode 12or the frequency of discharge sparks generated between the wireelectrode 12 and the workpiece 14.

The average voltage of the wire electrode 12 during the relativemovement of the wire electrode 12 or the frequency of discharge sparksgenerated between the wire electrode 12 and the workpiece 14 may bemonitored by a monitoring unit that is provided for the machine 10. Themonitoring unit may be included in, for example, the processor 52, as afunctional unit for monitoring at least one of the average voltage ofthe wire electrode 12 and the frequency of discharge sparks generatedbetween the wire electrode 12 and the workpiece 14. Alternatively, themachining control unit 62 may be configured to monitor the averagevoltage of the wire electrode 12 and the frequency of the dischargesparks generated between the wire electrode 12 and the workpiece 14.

When the path determination unit 64 detects the boundary line 68 whilethe wire electrode 12 is being moved relative to the workpiece, the pathcompensator 66 may compensate the machining path 16 based on thedetection result. Then, when the path compensator 66 has compensated themachining path 16, the drive control unit 58 may move the wire electrode12 relative to the workpiece along the compensated machining path 16from that point of time, even in the middle of the relative movement ofthe wire electrode 12 along the machining path 16 before beingcompensated.

Further, after compensation of the machining path 16, the drive controlunit 56 may move the wire electrode 12 relative to the workpiece alongthe compensated machining path 16 until the machining step one stepbefore the final finishing step is completed. Thus, for example, evenwhen the operator forgets to specify the boundary line 68, the machiningpath 16 is compensated after the start of the relative movement of thewire electrode 12. Therefore, it is possible to suppress generation offlaws 92 around the steps in the workpiece 14.

Modified Example 1-4

The path determination unit 64 may set, as the position of the boundaryline 68, the position designated via the touch panel display unit 56.For example, before start of relative movement of the wire electrode 12,the machine 10 displays the CAD data stored in advance in the memory 54on the screen of the touch panel display unit 56 together with themachining path 16 of the machining program. The operator visually checksthe shape of the workpiece 14 and the machining path 16, and indicatesthe position of the boundary line 68 or the position of the intersection84 by touching the screen of the touch panel display unit 56. Thisallows the operator to select and set the position for compensating themachining path 16 at his/her own will.

Second Embodiment

Next, a second embodiment will be described. The second embodimentrelates to a machining program editor 94. The same elements as those inthe first embodiment are allotted with the same reference numerals, anddescription thereof will be omitted as appropriate.

FIG. 11 is a block diagram showing a configuration of the machiningprogram editor 94 according to the second embodiment.

The machining program editor 94 refers to a general device for editing amachining program, including creation of a new machining program, inwhich a machining path 16 desired by an operator is set. Hereinafter,the “machining program editor 94” is also simply referred to as the“editor 94”.

The editor 94 includes a control unit 96, an operation unit 98 and adisplay unit 100. The operation unit 98 is, for example, a keyboard, andis used by an operator to operate the editor 94. The display unit 100has, for example, a liquid crystal screen, and is used by an operator toconfirm the details of the machining program being edited.

The control unit 96 includes a processor 102 and a memory 104. Theprocessor 102 has, as a functional unit, a program editing unit 106 forediting a machining program in accordance with the operator's operation.The processor 102 further includes a path determination unit 108 thatdetermines the structure of the machining path 16 set in the machiningprogram edited by the program editing unit 106, and a path compensator110 that compensates the machining path 16 according to thedetermination result from the path determination unit 108.

FIG. 12 is a flowchart for explaining an example of a processing flow ofthe machining program editor 94 according to the second embodiment.

Now, an example of the processing flow of the editor 94 will bedescribed with reference to FIG. 12 . To simply description, the“machining path 16” described below is the same as that of the firstembodiment, and the “workpiece 14” described below has the sameconfiguration as that of the first embodiment.

The editor 94 starts a series of processing (START) when the operatorrequests the editor 94 to create a new machining program or edit anexisting machining program (START). In the present embodiment, it isassumed that the operator requests the editor 94 to newly create amachining program.

Upon receiving the request from the operator, the program editing unit106 of the editor 94 creates a new editing file for a machining program(step S11). When editing of an existing machining program is requested,the existing machining program is read as an editing file. Thereafter,the program editing unit 106 edits the machining program according tooperator's operation such that the machining path 16 desired by theoperator is set (step S12).

At step S11 or S12, the operator inputs data relating to the shape ofthe workpiece 14 to the editor 94. The “data relating to the shape ofthe workpiece 14” is, for example, CAD format data prepared in advanceby the operator prior to the work of editing the machining program. Whenthe data relating to the shape of the workpiece 14 is input, the editor94 stores the data in the memory 104. The input data relating to theshape of the workpiece 14 may be displayed, as appropriate, on thescreen of the display unit 100 while the operator is editing themachining path 16. Thus, the operator can edit the machining path 16while checking the shape of the workpiece 14.

After editing the machining program, the editor 94 performs a pathdetermination process (step S13). In the path determination process, theprogram editing unit 106 calls the path determination unit 108. The pathdetermination unit 108 determines whether or not the machining path 16of the edited machining program includes a linear path section thatcrosses the boundary line 68 between the thick portion 70 and the thinportion 72 of the workpiece 14.

As mentioned above, the shape of the workpiece 14 herein is the same asthat in the first embodiment (FIGS. 5 and 6 ). The machining path 16herein is also the same as that in the first embodiment (FIG. 6 ).Therefore, the path determination unit 108 determines that the machiningpath 16 of the edited machining program “includes a linear path sectioncrossing the boundary line 68”.

When the path determination unit 108 determines that a linear pathsection crossing the boundary line 68 is included, the pathdetermination unit 108 calls the path compensator 110. The pathcompensator 110 compensates the machining path 16 so as to form, in thethin portion 72 over a predetermined distance 76, a protrusion 74projecting outward from the boundary line 68 (step S14). Thereby, a partof the first linear path section 78 of the machining path 16 is replacedwith a compensated path section 86. Similarly, a part of the secondlinear path section 80 of the machining path 16 is replaced with acompensated path section 86′.

It is assumed that this compensated path section 86 is the same as thatin the first embodiment. That is, the compensated path section 86 is setso as to replace a part of the first linear path section 78. Thecompensated path section 86 starts from the intersection 84. Thecompensated path section 86 further includes, as a halfway point, afirst point 88 located on the outer side of the intersection 84, andincludes, as an end point, a second point 90 that is a point on thefirst linear path section 78 in the thin portion 72 and is separated bythe predetermined distance 76 from the intersection 84. In thisembodiment, the first point 88 resides on the boundary line 68.Therefore, a line segment connecting the intersection 84 and the firstpoint 88 is orthogonal to the first linear path section 78. Thecompensated path section 86 in this embodiment is the shortest routeformed by connecting the intersection 84, the first point 88 and thesecond point 90 in this order.

The compensated path section 86′ is similar to that of the firstembodiment. That is, the compensated path section 86′ is set so as toreplace a part of the second linear path section 80. The compensatedpath section 86′ ends at the intersection 84′. The compensated pathsection 86′ further includes, as a halfway point, a first point 88′located on the outer side of the intersection 84′, and includes, as astart point, a second point 90′ that is a point on the second linearpath section 80 in the thin portion 72 and is separated by thepredetermined distance 76 from the intersection 84′. In the presentembodiment, the first point 88′ resides on the boundary line 68.Therefore, a line segment connecting the intersection 84′ and the firstpoint 88′ is orthogonal to the second linear path section 80. Thecompensated path section 86′ in this embodiment is the shortest routeformed by connecting the second point 90′, the first point 88′ and theintersection 84′, in this order.

The path compensator 110 outputs information on the compensatedmachining path 16 to the program editing unit 106. When receiving thecompensated machining path 16 from the path compensator 110, the programediting unit 106 automatically edits the machining program. Thisautomatic editing edits the machining program so that the wire electrode12 is moved relative to the workpiece along the compensated machiningpath 16 until the machining step one step before the final finishingstep is completed. The machining program is edited so that the wireelectrode 12 is moved relative to the workpiece along the originalmachining path 16 at the final finishing step.

The program editing unit 106 stores the machining program thusautomatically edited into the memory 104 in such a state that it can beoutput to the outside (step S15). Thus, the editing of the machiningprogram and the compensation process of the machining path 16 arecompleted (END).

The operator inputs the machining program stored in the memory 104 to awire electrical discharge machine 10′ (hereinafter, machine 10′), andperforms machining of the workpiece 14. Here, the machine 10′ may notinclude the path determination unit 64 and the path compensator 66included in the machine 10 of the first embodiment.

The machine 10′ runs the machining program edited by the editor 94 ofthe present embodiment so as to form the protrusions 74 and 74′ in thethin portion 72 of the workpiece 14 at the stage where the machining iscompleted up to the machining step one step before the final finishingstep. Then, the machine 10′ removes the protrusions 74 and theprotrusions 74′ at the final finishing step. Thus, the machine 10′ canperform machining on the workpiece 14 while suppressing generation offlaws 92 around the steps of the workpiece 14 similarly to the machine10 of the first embodiment.

As described above, according to the machining program editor 94 of thepresent embodiment, it is possible to edit a machining program capableof performing electrical discharge machining while suppressinggeneration of the flaws 92 around the steps of the workpiece 14.

Modified Example 2-1

Similarly to the modified example 1-1, the shape of the base of theprotrusion 74 may be changed. For example, the path compensator 110 maycompensate the machining path 16 so that the shape of the base of theprotrusion 74 formed by running the edited machining program has a shapeillustrated in FIG. 10A or FIG. 10B described in the modified example1-1. Thereby, similarly to the first embodiment, it is possible tosuppress generation of flaws 92 on the workpiece 14.

Modified Example 2-2

The program editing unit 106 may edit the machining program so as tocause the electrode 12 to move relative to the workpiece along thecompensated machining path 16 until a predetermined machining step, andthen move along the original machining path 16 at the machining stepsafter the predetermined machining step. The “predetermined machiningstep” may include, among the plurality of machining steps, the finalroughing step to the finishing step one step before the final finishingstep, as in the modified example 1-4.

Modified Example 2-3

The path determination unit 108 of the editor 94 may set the positiondesignated via the touch panel display unit 56 at the path determinationprocess (step S13), as the position of the boundary line 68. This allowsthe operator to select and set the position for compensating themachining path 16 at his/her own will.

Modified Example 2-4

The above embodiments and modified examples may be appropriatelycombined as long as no technical inconsistency occurs.

[Invention Obtained from the Embodiment]

Inventions that can be grasped from the above-described embodiments andmodified examples will be described below.

<First Invention>

A wire electrical discharge machine (10) that machines a workpiece (14)using a wire electrode (12) includes: a drive control unit (58)configured to move the wire electrode (12) relative to the workpiece(14) along a machining path (16) set in a machining program; a pathdetermination unit (64) configured to determine whether or not themachining path (16) includes a linear path section (78, 80) that crossesa boundary line (68) between a thick portion (70) of the workpiece (14)and a thin portion (72) of the workpiece (14), a thickness of the thinportion being smaller than a thickness of the thick portion (70) in anextending direction of the wire electrode (12); and a path compensator(66) configured to compensate the machining path (16) so as to form, inthe thin portion (72) over a predetermined distance (76), a protrusion(74, 74′) projecting outward from the boundary line (68) when the pathdetermination unit determines that the linear path section (78, 80) isincluded.

Thereby, it is possible to provide a wire electrical discharge machine(10) that can perform electrical discharge machining on a workpiece (14)while suppressing generation of flaws (92) around steps of the workpiece(14).

The path compensator (66) may be configured to compensate the machiningpath (16) so as to gradually change an amount of removal per unit timeof the workpiece (14) when the protrusion (74, 74′) is machined andremoved from the workpiece (14). Thereby, even after the wire electrode(12) has passed through the boundary line (68) along the originalmachining path (16), a sudden change of the removal amount per unit timeof the workpiece 14 can be avoided.

The machining on the workpiece (14) may include a plurality of machiningsteps that perform electrical discharge machining while moving the wireelectrode (12) relative to the workpiece (14) along the machining path(16), and the drive control unit (58) may be configured to move the wireelectrode (12) relative to the workpiece (14) along the machining path(16) compensated by the path compensator (66) up to a predeterminedmachining step among the plurality of machining steps, and move the wireelectrode (12) relative to the workpiece (14) along the machining path(16) before being compensated by the path compensator (66), in themachining steps after the predetermined machining step. Thus, theprotrusion (74, 74′) is removed at the predetermined machining step.

The predetermined machining step may be the machining step one stepbefore a final finishing step, or a roughing step. As a result, theprotrusion (74, 74′) is removed at the predetermined machining step.Also, by allowing the protrusion (74, 74′) to be removed at a stageprior to the final finishing step, it is possible to reduce the risk ofthe trace of the protrusion (74, 74′) remaining on the finishedworkpiece (14).

The protrusion (74, 74′) may have a substantially triangular shapehaving, as vertices, an intersection (84, 84′) between the linear pathsection (78, 80) and the boundary line (68), a first point (88, 88′)located on a line extending orthogonally to the linear path section (78,80) from the intersection (84, 84′), and a second point (90, 90′)located on the machining path (16) and separated by the predetermineddistance (76) from the intersection (84, 84′). This configuration makesit possible to gradually change the amount of removal per unit time ofthe workpiece (14) when removing the protrusion (74, 74′).

The path determination unit (64) may be configured to detect a positionof the boundary line (68) based on a shape of the workpiece (14). Thisenables the determination unit (64) to determine whether or not themachining path (16) includes a linear path section (78, 80) crossing theboundary line (68) between the thick portion (70) and the thin portion(72).

The path determination unit (64) may be configured to detect a positionof the boundary line (68) while the wire electrode (12) is movingrelative to the workpiece (14) along the machining path (16) to machinethe workpiece (14), based on an average voltage of the wire electrode(12), or a frequency of discharge sparks generated between the wireelectrode (12) and the workpiece (14). Thereby, for example, even whenthe operator forgets to specify the boundary line (68), the machiningpath (16) can be compensated after the start of the relative movement ofthe wire electrode (12).

<Second Invention>

A machining program editor (94) that edits a machining program in whicha machining path (16) for a wire electrode (12) of a wire electricaldischarge machine (10, 10′) is set, includes: a path determination unit(108) configured to determine whether or not the machining path (16)includes a linear path section (78, 80) that crosses a boundary line(68) between a thick portion (70) of a workpiece (14) and a thin portion(72) of the workpiece (14), a thickness of the thin portion beingsmaller than a thickness of the thick portion (70) in an extendingdirection of the wire electrode (12); and a path compensator (110)configured to compensate the machining path (16) so as to form, in thethin portion (72) over a predetermined distance (76), a protrusion (74,74′) projecting outward from the boundary line (68) when the pathdetermination unit determines that the linear path section (78, 80) isincluded.

Thereby, it is possible to provide a machining program editor (94) thatcan edit the machining program so as to perform electrical dischargemachining on a workpiece (14) while suppressing generation of flaws (92)around steps of the workpiece (14).

The path compensator (110) may be configured to compensate the machiningpath (16) so as to gradually change an amount of removal per unit timeof the workpiece (14) when the protrusion (74, 74′) is machined andremoved from the workpiece (14). Thereby, even after the wire electrode(12) has passed through the boundary line (68) along the originalmachining path (16), a sudden change of the removal amount per unit timeof the workpiece 14 can be avoided.

The machining program editor may further include a program editing unit(106) configured to edit the machining program. The machining on theworkpiece (14) may include a plurality of machining steps that performelectrical discharge machining while moving the wire electrode (12)relative to the workpiece (14) along the machining path (16), and theprogram editing unit (106) may be configured to edit the machiningprogram so as to cause the wire electrode (12) to move relative to theworkpiece (14) along the machining path (16) compensated by the pathcompensator (110) up to a predetermined machining step among theplurality of machining steps, and cause the wire electrode (12) to moverelative to the workpiece (14) along the machining path (16) beforebeing compensated compensated by the path compensator (110), in themachining steps after the predetermined machining step. Thus, theprotrusion (74, 74′) is removed at the predetermined machining step.

The predetermined machining step may be the machining step one stepbefore a final finishing step, or a roughing step. As a result, theprotrusion (74, 74′) is removed at the predetermined machining step.Also, by allowing the protrusion (74, 74′) to be removed at a stageprior to the final finishing step, it is possible to reduce the risk ofthe trace of the protrusion (74, 74′) remaining on the finishedworkpiece (14).

The protrusion (74, 74′) may have a substantially triangular shapehaving, as vertices, an intersection (84, 84′) between the linear pathsection (78, 80) and the boundary line (68), a first point (88, 88′)located on a line extending orthogonally to the linear path section (78,80) from the intersection (84, 84′), and a second point (90, 90′)located on the machining path (16) and separated by the predetermineddistance (76) from the intersection (84, 84′). This configuration makesit possible to gradually change the amount of removal per unit time ofthe workpiece (14) when removing the protrusion (74, 74′).

The path determination unit (108) may be configured to detect a positionof the boundary line (68) based on a shape of the workpiece (14). Thisenables the determination unit (108) to determine whether or not themachining path (16) includes a linear path section (78, 80) crossing theboundary line (68) between the thick portion (70) and the thin portion(72).

The machining program editor (94) may further comprise an operation unit(98) configured to allow an operator to operate the machining programeditor, and the path determination unit (108) be configured to set, as aposition of the boundary line (68), a position designated through theoperation unit (98). This allows the operator to select and set theposition for compensating the machining path (16) at his/her own will.

What is claimed is:
 1. A machining program editor that edits a machiningprogram in which a machining path for a wire electrode of a wireelectrical discharge machine is set, the machining program editorcomprising: a path determination unit configured to determine whether ornot the machining path includes a linear path section that crosses aboundary line between a thick portion of a workpiece and a thin portionof the workpiece, a thickness of the thin portion being smaller than athickness of the thick portion in an extending direction of the wireelectrode; and a path compensator configured to compensate the machiningpath so as to form, in the thin portion over a predetermined distance, aprotrusion projecting outward from the boundary line when the pathdetermination unit determines that the linear path section is included.2. The machining program editor according to claim 1, wherein the pathcompensator is configured to compensate the machining path so as togradually change an amount of removal per unit time of the workpiecewhen the protrusion is machined and removed from the workpiece.
 3. Themachining program editor according to claim 1, further comprising aprogram editing unit configured to edit the machining program, wherein:the machining on the workpiece includes a plurality of machining stepsthat perform electrical discharge machining while moving the wireelectrode relative to the workpiece along the machining path; and theprogram editing unit is configured to edit the machining program so asto cause the wire electrode to move relative to the workpiece along themachining path compensated by the path compensator up to a predeterminedmachining step among the plurality of machining steps, and cause thewire electrode to move relative to the workpiece along the machiningpath before being compensated by the path compensator, in the machiningsteps after the predetermined machining step.
 4. The machining programeditor according to claim 3, wherein the predetermined machining step isthe machining step one step before a final finishing step, or a roughingstep.
 5. The machining program editor according to claim 1, wherein theprotrusion has a substantially triangular shape having, as vertices, anintersection between the linear path section and the boundary line, afirst point located on a line extending orthogonally to the linear pathsection from the intersection, and a second point located on themachining path and separated by the predetermined distance from theintersection.
 6. The machining program editor according to claim 1,wherein the path determination unit is configured to detect a positionof the boundary line based on a shape of the workpiece.
 7. The machiningprogram editor according to claim 1, further comprising an operationunit configured to allow an operator to operate the machining programeditor, wherein the path determination unit is configured to set, as aposition of the boundary line, a position designated through theoperation unit.